Great game!
I like the enemy design with the eyes a lot. I think the enemies could maybe move a bit more unpredictably and it would be cool to be able to hold right click instead of having to spam, but the core gameplay is very fun.
Maybe the bullets shouldn't go through the crystal so you can't just stay right next to the crystal the entire time, but despite these minor details it's a really neat defending game for a 72 hour game jam!